According to first principles, especies living in very homogeneous environments under strong resource limitations, such as in the deep part of caves, should adjust their thermal tolerances to their surrounding temperature. We tested this with a group of cave beetles originally living in the Pyrenees at 4-11ºC, but of which one lineage moved to the coast of Catalonia during the early Pliocene and are now living at ca. 14-16ºC. Contrary to expectations, we found that these beetles have apparently lost their regulatory capabilities, and all of them seem to survive without problems between close to the freezing temperature of water and ca. 20ºC. This common upper thermal limit of 20ºC is above the temperatures they have experienced through the last 20MY of their evolutionary history. The observed capability to sustain temperatures higher than those experienced in their current (or past) environments, even in species which a priori should show a close adjustment, cast doubts on the predictions of the effect of temperature changes when they are not substantiated by physiological data.

Reference Article: Rizzo, V., Sánchez-Fernández D., Fresneda, J., Cieslak, A., Ribera, I. 2015. Lack of evolutionary adjustment to ambient temperature in highly specialized cave beetles. BMC Evolutionary Biology 2015, 15:10  doi:10.1186/s12862-015-0288-2

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